Charge control device

ABSTRACT

A charge control device includes a switching regulator that charges a capacitor with electricity supplied from a power supply. The charge control device is characterized in that feedback unit that feedback-inputs a predetermined control amount to the switching regulator is provided, and the switching regulator includes a control unit that controls a charge current supplied to the capacitor in accordance with the control amount feedback-input from the feedback unit.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to Japanese Patent ApplicationNo. 2017-108216, filed May 31, 2017, the entire contents of which areincorporated herein by reference.

FIELD

The present invention relates to a charge control device.

BACKGROUND

Conventionally, a drive recorder for photographing a situation around avehicle or inside the vehicle by an image pickup apparatus such as acamera or the like mounted on the vehicle and for recording photographedimages is known. Through the drive recorder, the situation around thevehicle or inside the vehicle can be recorded as images when apredetermined phenomenon such as an impact or the like has occurred, forexample. The drive recorder includes a power supply for backup in somecases so that, even if disconnection with a battery that supplies poweris caused by the impact which has occurred, for example, a predeterminedoperation can be performed.

Examples of the power supply for backup included in the drive recorderinclude an electric double-layer capacitor (hereinafter referred to alsoas an “EDLC”) also called an Ultracapacitor or a Supercapacitor, forexample. Since the EDLC can relatively improve a power storage amount ofelectric energy, saving/storing of the recorded images in a removablememory (an SD card, for example) or image photographing andrecording/storing after occurrence of the impact are made possible.

With the recent improvement in functions and performances of the driverecorder, a drive recorder including the EDLC as a power supply forbackup has spread. Prior-art documents describing an art relating to theart explained in the Description include one following patent documents.

[Patent Document 1] Japanese Patent Laid-open No. 2016-46993

[Patent Document 2] Japanese Patent Laid-open No. 2016-54628

SUMMARY

In an electronic equipment such as a drive recorder or the likeincluding an EDLC as a power supply for backup, the electricity(electric charge) charged during an operation needs to be discharged toan empty state at transition to a non-operation state in order tosuppress deterioration of the EDLC. Thus, at start of the operation, theEDLC needs to be quickly charged from the empty state to the electricityamount capable of backup for the operation of the electronic equipmentby using the electricity supplied from a battery.

In a charge circuit by a linear regulation type, a heat generationamount is high and a circuit loss is large and thus, it is difficult tohandle the quick charge period to the EDLC. In a charge circuit by aswitching type, a function of supplying a constant current for chargingthe EDLC is needed. However, in the switching type, an exclusiveconstant current control function for suppressing low-harmonicoscillation at time division of the electricity supplied from thebattery or the like by switching on/off is provided and then, the EDLCneeds to be charged quickly while the electricity supplied from thebattery or the like is kept at a constant value or less. Since an ICincluding a switching-type charge circuit as above is not provided as ageneral-purpose type, a dedicated IC development has been in demand.

An object of the present invention is to provide an art of constantcurrent control capable of rapid charge of a capacitor.

An aspect of a disclosed art is exemplified by a charge control device.That is, the charge control device includes a switching regulator forcharging a capacitor with electricity supplied from a power supply. Thecharge control device is characterized by including feedback unit thatfeedback-inputs a predetermined control amount into the switchingregulator, and control unit included in the switching regulator, thecontrol unit controlling a charge current supplied to the capacitor inaccordance with the control amount feedback-input from the feedbackunit.

According to the one aspect of the disclosed art, the art of constantcurrent control capable of quick charge to the capacitor is provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing an example of a block configuration of acharge control device in an embodiment 1;

FIG. 2 is a diagram showing an example of charge current characteristicsof the embodiment 1;

FIG. 3 is a diagram showing an example of a block configuration of acharge control device in an embodiment 2;

FIG. 4 is a diagram showing an example of charge current characteristicsof the embodiment 2;

FIG. 5 is a diagram showing an example of a block configuration of acharge control device in an embodiment 3;

FIG. 6 is a diagram showing an example of charge current characteristicsof the embodiment 3;

FIG. 7 is a diagram showing an example of a block configuration of acharge control device in an embodiment 4;

FIG. 8A is a diagram showing an example of charge currentcharacteristics of the embodiment 4;

FIG. 8B is a diagram showing an example of charge currentcharacteristics of the embodiment 4;

FIG. 9 is a diagram showing an example of a block configuration of acharge control device in an embodiment 5;

FIG. 10 is a diagram showing an example of charge currentcharacteristics of the embodiment 5;

FIG. 11 is a diagram showing an example of a block configuration of acharge control device in an embodiment 6;

FIG. 12 is a diagram showing an example of charge currentcharacteristics of the embodiment 6;

FIG. 13 is a diagram showing an example of charge currentcharacteristics of the embodiment 6;

FIG. 14 is a diagram showing an example of a block configuration of acharge control device in a variation;

FIG. 15 is a diagram for explaining the charge current characteristicsof the variation; and

FIG. 16 is a diagram for explaining the charge current characteristicsof the variation.

DESCRIPTION OF EMBODIMENTS

A charge control device according to an embodiment will be describedbelow by referring to the attached drawings. Configurations of theembodiments below are exemplifications, and the charge control device isnot limited to the configurations of the embodiments.

EMBODIMENTS Embodiment 1 Block Configuration

FIG. 1 is a diagram showing an example of a block configuration of acharge control device 10 according to the embodiment. The charge controldevice 10 exemplified in FIG. 1 is a charge control device included in apower receiving unit of an onboard apparatus that can be mounted on avehicle such as a drive recorder, for example. The onboard apparatus isconnected to a battery mounted on the vehicle through the powerreceiving unit. The power receiving unit converts electricity suppliedfrom the connected battery to a predetermined DC voltage and supplies itto a device such as a memory, a processor and the like provided in theonboard apparatus. Moreover, the power receiving unit includes a powersupply for backup. The processor or the like in the onboard apparatususes the electricity supplied through the power receiving unit andexecutes various programs stored in the memory or the like. By executingthe various programs, a situation around the vehicle or inside thevehicle is photographed by an image pickup apparatus such as a camera orthe like mounted on the vehicle, and the photographed images arerecorded.

As an onboard apparatus ether than the drive recorder, an audio visualnavigation integrated machine (AVN machine) providing various functionsincluding a navigation function, an audio function, an imagereproduction function, and a communication function, for example, to anoccupant is exemplified. In the following explanation, an onboardapparatus example including the charge control device 10 in the powerreceiving unit is assumed to be a drive recorder.

In FIG. 1, a capacitor C1 and a diode element D1 constitute a powersupply for backup provided in the power receiving unit of the onboardapparatus. An electricity supply form of the power receiving unit shownin FIG. 1 is an example of a form including a “Primary Power Supply 20”for converting supply electricity supplied from a battery to apredetermined DC voltage and a “System Power Supply 21” for convertingthe DC voltage converted by the “Primary Power Supply 20” to that foreach device in the onboard apparatus. In the following the “PrimaryPower Supply 20” is also called a “first power supply 20”, and the“System Power Supply 21” is also called a “secondary power supply 21”.

The capacitor C1 constituting the power supply for backup is a capacitorsuch as EDLC or the like, for example, and the diode element D1 is aSchottky barrier diode or the like. The capacitor C1 has polarity, and anegative electrode side is grounded to GND of the vehicle on which it ismounted, while a positive electrode side is connected to an anode of thediode element D1. A cathode of the diode element D1 is connected to aninput end of the secondary power supply 21. To the input end of thesecondary power supply 21, the predetermined DC voltage converted by theprimary power supply is applied. In the power supply for backup shown inFIG. 1, in the case of disconnection between the battery and the primarypower supply 20 or in the case of disconnection between the primarypower supply 20 and the secondary power supply 21, for example, theelectricity charged in the capacitor C1 is supplied as the electricitywith a constant voltage to the secondary power supply 21 through thediode element D1.

Charge Control Operation

The charge control device 10 according to the embodiment includes atleast a switching regulator 11, an inductor element L1, resistances R1and R2. The switching regulator 11 is a switching regulator of ageneral-purpose current mode type. The switching regulator 11 hasterminals “VIN”, “GND”, “OUT”, “FB”, “SS”, and “COMP”.

The VIN terminal of the switching regulator 11 is connected to an outputend of the primary power supply 20, and the GND terminal is grounded tothe GND of the vehicle. Moreover, the OUT terminal of the switchingregulator 11 is connected to the other end of the inductor element L1with one end connected to the anode of the capacitor C1 constituting thepower supply for backup.

In the switching regulator 11, the supply electricity of the primarypower supply 20 input into the VIN terminal is subjected to timedivision of a PWM (Pulse Width Modulation) method, and the time-dividedelectricity is output to the OUT terminal. The electricity output to theOUT terminal charges the capacitor C1 through the inductor element L1.

The switching regulator 11 of the current mode type includes an internalcurrent source 11 a, an error amplifier (Error Amp) 11 b, a slopecompensation unit 11 c, a comparator (PWM Comp) 11 d, a PWM control unit(PWM Control Logic) 11 e, and switching elements SW1 and SW2 as aninternal configuration.

The switching elements SW1 and SW2 are semiconductor devices such as aMOSFET (Metal-Oxide-Semiconductor Field-Effect-Transistor) or the like,for example. In FIG. 1, the switching element SW1 is constituted by aP-type MOSFET, the switching element SW2 is constituted by an N-typeMOSFET. A source of the switching element SW1 is connected to the VINterminal, and a drain is connected to a drain of the switching elementSW2. A source of the switching element SW2 is connected to a GNDterminal. A gate of each of the switching elements SW1 and SW2 isconnected to the PWM control unit 11 e.

The PWM control unit 11 e generates a gate control signal determining anON state and an OFF state of the switching elements SW1 and SW2 on thebasis of an output value of the comparator 11 d connected to itself andan input clock signal (CLK) of a predetermined cycle. Here, the ON stateis a state indicating a logical value H (5 V, for example) which is avoltage value exceeding a gate threshold value voltage of each switchingelement, and the OFF state is a state indicating a logical value L (0 V,for example) which is a voltage value smaller than the gate thresholdvalue voltage of each switching element. The switching elements SW1 andSW2 electrically connect the source and the drain when the gate controlsignal is in the ON state and disconnect the source and the drain in theOFF state.

The switching regulator 11 controls switching operations of theswitching elements SW1 and SW2 by controlling a period of the ON state(hereinafter referred to also as an “ON period”) of the gate controlsignal and a period of the OFF state (hereinafter referred to also as an“OFF period”) through the PWM control unit 11 e.

In the switching regulator 11 of the current mode type, the ON/OFFstate, ON period, and OFF period of the gate control signal aredetermined through the error amplifier 11 b, the slope compensation unit11 c, and the comparator 11 d.

The slope compensation unit 11 c detects a peak value of a current ISWflowing between the VIN terminal and the source of the switching elementSW1 during the switching operations of the switching elements SW1 andSW2. Then, the slope compensation unit 11 c converts the current ISWdetected by using conductance (gain value (Gcs)) set in advance to avoltage signal.

The slope compensation unit 11 c generates a slope waveform whichbecomes a standard of the PWM control in a current mode on the basis ofthe voltage signal converted from the current ISW and an offset voltage(Voffset). In the generated slope waveform, a slope compensation signal(Slope Compensation) is reflected. The slope compensation unit 11 csuppresses low-harmonic oscillation by a phase difference in a voltagechange and a current change during the switching operation by reflectingthe slope compensation signal (a ramp wave, for example) in the slopewaveform generated on the basis of the voltage signal converted from thecurrent ISW and the offset voltage (Voffset).

The slope compensation unit 11 c outputs the slope waveform in which theslope compensation signal is reflected to an inverted terminal of thecomparator 11 d. An error signal output from the output terminal of theerror amplifier 11 b is input into a non-inverted input terminal of thecomparator 11 d.

The comparator 11 d compares a voltage value of the slope waveform inputinto the inverted terminal and a voltage value of the error signal inputinto the non-inverted terminal and outputs a comparison result to theoutput terminal. If the voltage value of the slope waveform input intothe non-inverted input terminal is higher than the voltage value of theerror signal input into the inverted terminal, for example, a statussignal of the logical value H is output. On the other hand, if thevoltage value of the slope waveform input into the non-inverted inputterminal is lower than the voltage value of the error signal input intothe inverted terminal, a status signal of the logical value L is output.

In the PWM control unit 11 e connected to the output terminal of thecomparator 11 d, a gate control signal that controls the switchingoperations of the switching elements SW1 and SW2 is generated on thebasis of the state of the logical value of the status signal and theperiods during which the respective logical values continue.

The error amplifier 11 b is an error amplifier including an invertedinput terminal and two non-inverted input terminals. The inverted inputterminal of the error amplifier 11 b is connected to the FB terminalwhich is a negative feedback input terminal in the switching regulator11. In the switching regulator 11, a reference voltage VREF is connectedto one of the non-inverted input terminals of the error amplifier 11 b,while the SS terminal is connected to the other non-inverted inputterminal.

The internal current source 11 a connected to the S3 terminal (softstart terminal) is a power supply for causing a soft start function inthe switching regulator 11 to function. A soft start period isdetermined in accordance with a capacity of a capacitor Ct connected tothe SS terminal outside the switching regulator 11 and a current amountsupplied from the internal current source 11 a. The output terminal ofthe error amplifier 11 b is connected to the non-inverted input terminaland the COMP terminal of the comparator 11 d.

In the switching regulator 11 according to the embodiment, the outputvoltage of the error amplifier 11 b is divided through the resistancesR1 and R2 connected to the COMP terminals outside the switchingregulator 11, and the divided output voltage is feedback-input into theFB terminal as a bias voltage. The resistances R1 and R2 constitutevoltage dividing resistances. One end of the voltage dividing resistanceR1 is connected to the COMP terminal, while the other end is connectedto the FB terminal. The other end of the voltage dividing resistance R1connected to the FB terminal is connected to the other end of thevoltage dividing resistance R2 with one end grounded to the GND of thevehicle.

In the switching regulator 11 according to the embodiment, an outputvoltage (Vcomp) of the error amplifier 11 b divided by the voltagedividing resistances (R1, R2) through the FB terminal is input as thefeedback voltage into the inverted input terminal of the error amplifier11 b.

The error amplifier 11 b amplifies a differential voltage (error)between the feedback voltage input into the FB terminal and thereference voltage VREF by a predetermined gain (A) and outputs theamplified differential voltage as an error signal to the outputterminal. The output voltage (Vcomp) of the error amplifier 11 b isoutput to the COMP terminal of the switching regulator 11.

Here, a voltage relationship between the output voltage (Vcomp) outputto the COMP terminal and the reference voltage VREF is expressed by theformula (1) shown below:

$\begin{matrix}{{Vcomp} = {\frac{{R\; 1} + {R\; 2}}{R\; 2} \times {{VREF}\left( {{{calculated}\mspace{14mu} {as}\mspace{14mu} A} = \infty} \right)}}} & {{Formula}\mspace{14mu} (1)}\end{matrix}$

As indicated in the formula (1), by setting a value of the voltagedividing resistance (R1, R2) connected to the COMP terminal in advancein accordance with the predetermined gain (A) of the error amplifier 11b and the reference voltage VREF, for example, an arbitrary voltageaccording to the voltage dividing resistance (R1, R2) value can beoutput to the output terminal of the error amplifier 11 b.

As described above, in the switching regulator 11, the gate controlsignal is generated by a comparison result between the voltage value ofthe slope waveform input into the inverted terminal of the comparator 11d and the output voltage value of the error amplifier 11 b input intothe non-inverted terminal. Thus, in the charge control device 10according to the embodiment, the current ISW flowing between the sourceand the drain electrically conducted in the ON period of the switchingelement SW1 can be controlled by controlling the output voltage (Vcomp)of the error amplifier 11 b of the switching regulator 11, for example.

Here, a relationship between the current ISW and the output voltage(Vcomp) of the error amplifier 11 b is expressed by the followingformula (2):

ISW (peak)=Gcs×(Vcomp−Voffset)  Formula (2)

※ISW (peak)=Peak value of the ripple current in ISW

As shown in the formula (2), the charge control device 10 according tothe embodiment can control the value of the current ISW flowing inbetween the source and the drain during the ON period of the switchingelement SW1 of the switching regulator 11 to a constant current valueaccording to the reference voltage VREF and the voltage dividingresistance (R1, R2) values. The switching regulator 11 of the chargecontrol device 10 can supply the current ISW according to accuracy ofthe reference voltage VREF to the capacitor C1. According to the chargecontrol device 10 according to the embodiment, charging can be performedwhile the charge current supplied to the capacitor is controlled to aconstant value by using the general-purpose switching regulator with alarge communication amount.

Moreover, an additional circuit added to the switching regulator 11 isconstituted by voltage dividing resistance (R1, R2) dividing the outputvoltage (Vcomp) of the error amplifier 11 b output from the COMPterminal. Thus, size reduction and cost reduction are made possible inthe onboard apparatus such as a drive recorder or the like including thecharge control device 10 according to the embodiment.

Charge Current Characteristics

FIG. 2 exemplifies charge current characteristics of the switchingregulator 11. The charge current characteristics in FIG. 2 are a resultof simulation analysis of the charge control device 10 shown in FIG. 1,assuming that the input voltage of the VIN terminal as “5 V”, thereference voltage VREF is “0.8 V”, the gain value (Gcs) is “0.222 V/A”,the offset voltage (Voffset) is “0.3 V”, the slope compensation signalis “1.34 A/cycle”, the voltage dividing resistance R1 is “1 kΩ”, thevoltage dividing resistance R2 is “220 kΩ”, and the inductor element L1is “2.2 μH”. The gain value (Gcs) is a gain value, assuming that animpedance Ron is “100 kΩ” and an impedance DCR of the inductor elementL1 is “140 kΩ” in the switching regulator 11 when the switching elementSW1 is ON.

In FIG. 2, a graph g1 shows a temporal change of an average value (Iin)of the current ISW flowing between the VIN terminal and the source ofthe switching element SW1 when the switching elements SW1 and SW2 are inoperation. Similarly, a graph g2 shows a temporal change of the chargevoltage value (Vout) of the capacitor C1 and a graph g3 shows a temporalchange of the current value (Iout) supplied to the capacitor C1 throughthe inductor element L1. A vertical axis in FIG. 2 indicates a currentvalue (0.5 A/div) and a voltage value (1 V/div), while a lateral axisindicates normalized time elapse. A broken line in parallel with thelateral axis indicates a 0 V standard and a 0 A standard in FIG. 2.

As shown in the graph g2, the charge voltage value (Vout) of thecapacitor C1 is changed so as to gently rise with the time elapse fromstart of the switching operation and reaches the constant voltage valuedetermined by the charge capacity of the capacitor C1. Moreover, asshown in the graph g1, the current value (Iin) flowing into theswitching regulator 11 during the switching operation gently rises withthe time elapse from the start of the switching operation and reaches aconstant state within a range from 0.9 A to 1.0 A. From the relativetemporal changes in the graph g1 and the graph g2, it is known that thecurrent value (Iin) flowing into the switching regulator 11 reaches theconstant state within the range from 0.9 A to 1.0 A in the vicinity ofthe full-charged capacity or the capacitor C1. It is known that thecharge control device 10 shown in FIG. 1 performs the charge operationwhile the current value (Iin) flowing into the switching regulator 11 issuppressed to the constant state according to the charge capacity of thecapacitor C1.

Moreover, as shown in a graph g3, the current value (Iout) supplied tothe capacitor C1 with the switching operation of the switching regulator11 gently decreases with the time elapse from the start of the switchingoperation and reaches the constant state within the range of 0.9 A to1.0 A. A hatched region in the graph g3 indicates a change margin of thecurrent value (Iout) pulsated with the switching operations of theswitching elements SW1 and SW2.

It is known that the current value (Iout) involved in the switchingoperation of the switching regulator 11 makes a temporal change so as tobecome the same value as the current value (Iin) having reached theconstant state in accordance with the charge capacity of the capacitorC1. It is known that the charge control device 10 shown in FIG. 1performs charging by decreasing the current value (Iout) with anincrease in the charge amount (charge voltage value (Vout)), while thecurrent value (Iout) exceeding 2A is supplied to the capacitor C1 at thestart of the switching operation.

Embodiment 2 Block Configuration

The form of the charge control device 10 described in the embodiment 1is a form in which the output voltage (Vcomp) output to the COMPterminal is input into the FB terminal as a bias voltage through thevoltage dividing resistance (R1, R2) grounded to the GND of the vehicle.In the charge control device 10, the output voltage (Vcomp) output tothe COMP terminal is divided through the voltage dividing resistance(R1, R2) pulled up to the power supply side, and the divided voltage maybe input into the FB terminal as the bias voltage.

In the form in which the voltage dividing resistance (R1, R2) is pulledup to the power supply side, the output voltage value output from theCOMP terminal can be set to a voltage value lower than the referencevoltage VREF. The charge control device 10 can relatively suppressintensity of the current value (Iin) flowing into the switchingregulator 11 during the switching operation as compared with the form ofthe charge control device 10 shown in FIG. 1 by performing the switchingoperation on the basis of the output voltage value set to a voltagevalue lower than the reference voltage VREF. In the form of theembodiment 2, the charge control device 10 which reduces a load to anelectricity supply capability on the onboard apparatus side can beprovided.

FIG. 3 is a diagram showing an example of a block configuration of thecharge control device 10 according to the embodiment 2 (hereinafterreferred to also as “the embodiment”). A form of the charge controldevice 10 shown in FIG. 3 is a form in which the output voltage (Vcomp)output to the COMP terminal is feed-back input into the FB terminalthrough the voltage dividing resistance (R1, R2) pulled up to theprimary power supply 20 side.

One end of the voltage dividing resistance R1 is connected to the COMPterminal, while the other end is connected to the FB terminal. Moreover,the other end of the voltage dividing resistance R1 connected to the FBterminal is connected to the other end of the voltage dividingresistance R2 with one end pull-up connected to the primary power supply20 side. In the block configuration shown in FIG. 3, the constitutionother than the voltage dividing resistance (R1, R2) is similar to theconstitution in FIG. 1. Hereinafter, the charge control operation of thecharge control device 10 of the embodiment will be described mainly onthe constitution different from that in FIG. 1.

Charge Control Operation

In the switching regulator 11 in the form shown in FIG. 3, the outputvoltage (Vcomp) of the error amplifier 11 b divided through the voltagedividing resistance (R1, R2) pull-up connected to the primary powersupply 20 side is input as the feedback voltage to the inverted inputterminal of the error amplifier 11 b.

The error amplifier 11 b amplifies the differential voltage (error)between the feedback voltage input into the FB terminal and thereference voltage VREF by the predetermined gain (A) and outputs theamplified differential voltage as an error signal to the outputterminal. The output voltage (Vcomp) of the error amplifier 11 b isoutput to the COMP terminal of the switching regulator 11.

In the form of the embodiment 2, the voltage relationship between theoutput voltage (Vcomp) output to the COMP terminal and the referencevoltage VREF is expressed by the formula (3) shown below:

$\begin{matrix}{{{Vcomp} = {{VREF} - {\frac{R\; 1}{R\; 2} \times \left( {{VIN} - {VREF}} \right)}}}\left( {{{calculated}\mspace{14mu} {as}\mspace{14mu} A} = \infty} \right)} & {{Formula}\mspace{14mu} (3)}\end{matrix}$

In the form of the second embodiment 2, too, by setting the value of thevoltage dividing resistance (R1, R2) connected to the COMP terminal inadvance in accordance with the predetermined gain (A) of the erroramplifier 11 b, the reference voltage VREF, and the voltage on theprimary power supply 20 side, an arbitrary voltage according to thevoltage dividing resistance (R1, R2) value can be output to the outputterminal of the error amplifier 11 b. In the charge control device 10,the current ISW flowing between the source and the drain electricallyconducted in the ON period of the switching element SW1 can becontrolled by controlling the output voltage (Vcomp) of the erroramplifier 11 b of the switching regulator 11.

Similarly to the embodiment 1, the relationship between the current ISWand the output voltage (Vcomp) of the error amplifier 11 b is expressedby the following formula (4):

ISW(peak)=Gcs×(Vcomp−Voffset)  Formula (4)

※ISW (peak)32 Peak value of the ripple current in ISW

As shown in the formula (4), in the form of the embodiment 2, too, thecharge control device 10 can control the value of the current ISWflowing in between the source and the drain during the ON period of theswitching element SW1 of the switching regulator 11 to a constantcurrent value according to the reference voltage VREF and the voltagedividing resistance (R1, R2) values pulled up to the power supply side.The switching regulator 11 of the charge control device 10 can supplythe current ISW according to accuracy of the reference voltage VREF tothe capacitor C1. In the charge control device 10 in the embodiment 2,too, a charge circuit capable of quick charge while the current chargedin the capacitor is controlled can be provided by using thegeneral-purpose switching regulator with a large communication amount.

Charge Current Characteristic

FIG. 4 exemplifies charge current characteristics of the switchingregulator 11. The charge current characteristics in FIG. 4 are a resultof simulation analysis of the charge control device 10 shown in FIG. 3,assuming that the input voltage of the VIN terminal is “5 V”, thereference voltage VREF is “0.8 V”, the gain value (Gcs) is “0.222 V/A”,the offset voltage (Voffset) is “0.3 V”, the slope compensation signalis “1.34 A/cycle”, the voltage dividing resistance R1 is “1 kΩ”, thevoltage dividing resistance R2 is “47 kΩ”, and the inductor element L1is “2.2 μH”. The gain value (Gcs) is similar to that in FIG. 2.

In FIG. 4, a graph g1 shows a temporal change of an average value (Tin)of the current ISW flowing between the VIN terminal and the source ofthe switching element SW1 during the switching operations of theswitching elements SW1 and SW2. A graph g2 shows a temporal change ofthe charge voltage value (Vout) of the capacitor C1 and a graph g3 showsa temporal change of the current value (Iout) supplied to the capacitorC1 through the inductor element L1. A vertical axis in FIG. 4 indicatesa current value (0.5 A/div) and a voltage value (1 V/div), while alateral axis indicates normalized time elapse. A broken line in parallelwith the lateral axis indicates the 0 V standard and the 0 A standard inFIG. 2.

Temporal change tendencies of the graphs g1, g2, and g3 shown in FIG. 4indicate change tendencies similar to those in the embodiment 1.However, the current value (Iin) flowing into the switching regulator 11during the switching operation reaches the constant state in thevicinity of 0.5 A. Moreover, the current value (Iout) supplied to thecapacitor C1 at the start of the switching operation lowers to thevicinity of 1.75 A.

When the temporal change tendencies of the graphs g1 to g3 shown in FIG.2 and the temporal change tendencies of the graphs g1 to g3 shown inFIG. 4 are compared, it is known that the relative intensities of thecurrent value (Iin) flowing into the switching regulator 11 during theswitching operation and the current value (Iout) supplied to thecapacitor C1 are suppressed. However, a period taken for charging thecapacitor C1 tends to be relatively longer by a relative decrease of thecurrent value (Iout) supplied to the capacitor C1.

Embodiment 3 Block Configuration

FIG. 5 is a diagram showing an example of a block configuration of thecharge control device 10 according to an embodiment 3 (hereinafterreferred to also as “the embodiment”). The charge control device 10shown in FIG. 5 is a form in which the charge voltage (Vout) charged inthe capacitor C1 is reflected as a feedback amount with respect to theform of the charge control device 10 described in the embodiment 1.

The charge control device 10 of the embodiment includes at least theswitching regulator 11, the inductor element L1, and resistances R1, R2,and R3. The resistances R1, R2, and R3 constitute voltage dividingresistances. In the block configuration shown in FIG. 5, theconstitution other than the voltage dividing resistances (R1, R2, R3) issimilar to the constitution in FIG. 1.

One end of the voltage dividing resistance R1 is connected to the COMPterminal, while the other end is connected to the FB terminal. The otherend of the voltage dividing resistance R1 connected to the FB terminalis connected to the other end of the voltage dividing resistance R2 withone end grounded to the GND of the vehicle. One end of the voltagedividing resistance R3 is connected to a positive electrode-sideterminal of the capacitor C1, while the other end is connected to theother end of the voltage dividing resistance R1 connected to the FBterminal.

In the charge control device 10 of the embodiment 3, the charge voltage(Vout) of the capacitor C1 is negative-feedback input into the invertedterminal of the error amplifier 11 b through the voltage dividingresistance R3, whereby the current value (Iin) flowing into theswitching regulator 11 during the switching operation can be controlledin accordance with the charged state of the capacitor C1. In the onboardapparatus such as a drive recorder or the like including the chargecontrol device 10 of the embodiment, for example, when the currentcapacity of the primary power supply 20 or the current amount capable ofsupply in the battery is limited, adjustment of the current value (Iin)flowing into the switching regulator 11 during the switching operationcan be made possible in accordance with the limited current amount.Hereinafter, the charge control operation of the charge control device10 in the embodiment will be described mainly on the constitutiondifferent from that in FIG. 1.

Charge Control Operation

In the switching regulator 11 in a form shown in FIG. 5, the chargevoltage (Vout) of the capacitor C1 divided through the voltage dividingresistance R3 and the output voltage (Vcomp) of the error amplifier 11 bdivided by the voltage dividing resistance (R1, R2) are input as thefeedback voltage into the inverted input terminal of the error amplifier11 b.

The error amplifier 11 b amplifies the differential voltage (error)between the feedback voltage input into the FB terminal and thereference voltage VREF by the predetermined gain (A) and outputs theamplified differential voltage as an error signal to the outputterminal. The output voltage (Vcomp) of the error amplifier 11 b isoutput to the COMP terminal of the switching regulator 11.

In the form of the embodiment 3, the voltage relationship between theoutput voltage (Vcomp) output to the COMP terminal and the referencevoltage VREF is expressed by the formula (5) shown below:

$\begin{matrix}{{{Vcomp} = {{VREF} + {R\; 1 \times \left( {\frac{VREF}{R\; 2} - \frac{{Vout} - {VREF}}{R\; 3}} \right)}}}\left( {{{calculated}\mspace{14mu} {as}\mspace{14mu} A} = \infty} \right)} & {{Formula}\mspace{14mu} (5)}\end{matrix}$

As shown in the formula (5), by setting each value of the voltagedividing resistances (R1, R2, R3) in advance in accordance with thepredetermined gain (A) of the error amplifier 11 b, a voltage accordingto the charge voltage (Vout) of the capacitor C1 can be output to theoutput terminal of the error amplifier 11 b. The charge control device10 can reflect the charge voltage (Vout) of the capacitor C1 in thecontrol of the current ISW flowing between the source and the drainelectrically conducted during the ON period of the switching element SW1by controlling the output voltage (Vcomp) of the error amplifier 11 b ofthe switching regulator 11.

Similarly to the embodiment 1, the relationship between the current ISWand the output voltage (Vcomp) output to the COMP terminal is expressedby the following formula (6):

ISW (peak)=Gcs×(Vcomp−Voffset)  Formula (6)

※ISW (peak)=Peak value of the ripple current in ISW

As shown in formula (6), the charge control device 10 of the embodimentcan control the value of the current ISW flowing in between the sourceand the drain during the ON period of the switching element SW1 of theswitching regulator 11 to the constant current value according to thereference voltage VREF and the voltage dividing resistance (R1, R2, R3)values.

Charge Current Characteristics

FIG. 6 is a diagram showing an example of the charge currentcharacteristics by the charge control device 10 of the embodiment. Thecharge current characteristics in FIG. 6 are a result of simulationanalysis of the charge control device 10 shown in FIG. 5, assuming thatthe input voltage of the VIN terminal is “5 V”, the reference voltageVREF is “0.8 V”, the gain value (Gcs) is “0.222 V/A”, the offset voltage(Voffset) is “0.3 V”, the slope compensation signal is “1.34 A/cycle”,the voltage dividing resistance R1 is “1 kΩ”, the voltage dividingresistance R2 is “220 kΩ”, the voltage dividing resistance R3 is “47kΩ”, and the inductor element L1 is “2.2 μH”. The gain value (Gcs) issimilar to that in FIG. 2.

In FIG. 6, a graph g1 shows a temporal change of an average value (Iin)of the current ISW flowing between the VIN terminal and the source ofthe switching element SW1 during the switching operations of theswitching elements SW1 and SW2. A graph g2 shows a temporal change ofthe charge voltage value (Vout) of the capacitor C1 and a graph g3 showsa temporal change of the current value (Iout) supplied to the capacitorC1 through the inductor element L1. A vertical axis in FIG. 6 indicatesa current value (0.5 A/div) and a voltage value (1 V/div), while alateral axis indicates normalized time elapse. A broken line in parallelwith the lateral axis indicates the 0 V standard and the 0 A standard.

As shown in the graph g1, the current value (Iin) flowing into theswitching regulator 11 during the switching operation gentlyrises/changes with the time elapse from the start of the switchingoperation and reaches the maximum value of approximately 0.7 A. Thecurrent value (Iin) after having reached the maximum value changes tothe constant state within the range from 0.7 A to 0.5 A or slightlydecreases with the time elapse.

It is known from relative temporal changes in the graph g1 and the graphg2 that the current value (Iin) reaches a maximum value when the chargedstate of the capacitor C1 is in the vicinity of approximately a half ofa full-charged capacity. Moreover, by comparing the temporal changetendency of the graph g1 shown in FIG. 2 with the temporal changetendency of the graph g1 shown in FIG. 4, it is known that relativeintensity of the current value (Iin) flowing into the switchingregulator 11 during the switching operation is suppressed. Moreover, itis known that a period taken for charging the capacitor C1 tends to berelatively longer by a relative decrease of the current value (Iout)supplied to the capacitor C1. The temporal change tendencies of thegraphs g2 and g3 shown in FIG. 6 show the change tendency similar tothat in the embodiment 1.

In the charge control device 10 in the embodiment, when the currentcapacity of the primary power supply 20 or the current amount capable ofsupply in the battery is limited, the capacitor C1 can be charged whilethe maximum value of the current value (Iin) flowing into the switchingregulator 11 during charging is suppressed in accordance with thecharged state.

Embodiment 4 Block Configuration

FIG. 7 is a diagram showing an example of a block configuration of thecharge control device 10 according to an embodiment 4 (hereinafterreferred to also as “the embodiment”). The charge control device 10shown in FIG. 7 is a form in which the charge voltage (Vout) charged inthe capacitor C1 is further reflected as a feedback amount with respectto the form of the charge control device 10 described in the embodiment2.

The charge control device 10 shown in FIG. 7 includes at least theswitching regulator 11, the inductor element L1, and resistances R1, R2,and R3 constituting the voltage dividing resistances. One end of thevoltage dividing resistance R1 is connected to the COMP terminal, whilethe other end is connected to the FB terminal. The other end of thevoltage dividing resistance R1 connected to the FB terminal is connectedto the other end of the voltage dividing resistance R2 with one endpull-up connected to the primary power supply 20 side. One end of thevoltage dividing resistance R3 is connected to the positiveelectrode-side terminal of the capacitor C1, while the other end isconnected to the other end of the voltage dividing resistance R1connected to the FB terminal. In the block configuration shown in FIG.7, the constitution other than the voltage dividing resistances (R1, R2,R3) is similar to the constitution in FIG. 3. Hereinafter the chargecontrol operation of the charge control device 10 of the embodiment willbe described mainly on the constitution different from that in FIG. 3.

Charge Control Operation

In the charge control device 10 of the embodiment 4, the current value(Iin) flowing into the switching regulator 11 during the switchingoperation can be controlled in accordance with the charged state of thecapacitor C1 by negative-feedback input of the charge voltage (Vout) ofthe capacitor C1 into the inverted terminal of the error amplifier 11 bthrough the voltage dividing resistance R3.

In the switching regulator 11 in the form shown in FIG. 7, the chargevoltage (Vout) of the capacitor C1 divided through the voltage dividingresistance R3 and the output voltage (Vcomp) of the error amplifier 11 bdivided by the voltage dividing resistance (R1, R2) pull-up connected tothe primary power supply 20 side are input as the feedback voltage intothe inverted input terminal of the error amplifier 11 b.

The error amplifier 11 b amplifies the differential voltage (error)between the feedback voltage input into the FB terminal and thereference voltage VREF by the predetermined gain (A) and outputs thesimplified differential voltage as an error signal to the outputterminal. The output voltage (Vcomp) of the error amplifier 11 b isoutput to the COMP terminal of the switching regulator 11.

In the form of the embodiment 4, the voltage relationship between theoutput voltage (Vcomp) output to the COMP terminal and the referencevoltage VREF and the relationship between the current ISW and the outputvoltage (Vcomp) of the error amplifier 11 b are expressed by the formula(7) shown below:

$\begin{matrix}{{{{Vcomp} = {{VREF} - {R\; 1 \times \left( {\frac{{VIN} - {VREF}}{R\; 2} - \frac{{Vout} - {VREF}}{R\; 3}} \right)}}}\mspace{20mu} \left( {{{calculated}\mspace{14mu} {as}\mspace{14mu} A} = \infty} \right)}\mspace{20mu} {{{ISW}({peak})} = {{Gcs} \times \left( {{Vcomp} - {Voffset}} \right)}}{{{ISW}\mspace{14mu} ({peak})} = {{Peak}\mspace{14mu} {value}\mspace{14mu} {of}\mspace{14mu} {the}\mspace{14mu} {ripple}\mspace{14mu} {current}\mspace{14mu} {in}\mspace{14mu} {ISW}}}} & {{Formula}\mspace{14mu} (7)}\end{matrix}$

In the form of the embodiment 4, too, the voltage according to thecharge voltage (Vout) of the capacitor C1 can be output to the outputterminal of the error amplifier 11 b by setting each value of thevoltage dividing resistances (R1, R2, R3) in advance in accordance withthe predetermined gain (A) of the error amplifier 11 b, the referencevoltage VREF, and the voltage on the primary power supply 20 side.

The charge control device 10 can reflect the charge voltage (Vout) ofthe capacitor C1 in the control of the current ISW flowing between thesource and the drain electrically conducted during the ON period of theswitching element SW1 by controlling the output voltage (Vcomp) of theerror amplifier 11 b of the switching regulator 11. The charge controldevice 10 can control the value of the current ISW flowing into thesource and the drain during the ON period of the switching element SW1of the switching regulator 11 to a constant current value according tothe reference voltage VREF and the voltage dividing resistance (R1, R2,R3) values.

Charge Current Characteristics

FIGS. 8A and 8B are a diagram showing an example of the charge currentcharacteristics by the charge control device 10 of the embodiment. Thecharge current characteristics in FIG. 8A are at result of simulationanalysis of the charge control device 10 shown in FIG. 7, assuming thatthe input voltage of the VIN terminal is “5 V”, the reference voltageVREF is “0.8 V”, the gain value (Gcs) is “0.222 V/A”, the offset voltage(Voffset) is “0.3 V”, the slope compensation signal is “1.34 A/cycle”,the voltage dividing resistance R1 is “1 kΩ”, the voltage dividingresistance R2 is “220 kΩ”, the voltage dividing resistance R3 is “47kΩ”, and the inductor element L1 is “2.2 μH”. Moreover, the chargecurrent characteristics in FIG. 8B are a simulation analysis result whenthe voltage dividing resistance R3 is set infinite in the variousconditions. The gain value (Gcs) is similar to that in FIG. 2.

In FIGS. 8A and 8B, a graph g1 snows a temporal change of an averagevalue (Iin) of the current ISW flowing between the VIN terminal and thesource of the switching element SW1 during the switching operations ofthe switching elements SW1 and SW2. A graph g2 shows a temporal chargeof the charge voltage value (Vout) of the capacitor C1 and a graph g3shows a temporal change of the current value (Iout) supplied to thecapacitor C1 through the inductor element L1. A vertical axis in each ofFIGS. 8A and 8B indicates a current value (0.5 A/div) and a voltagevalue (1 V/div), while a lateral axis indicates normalized time elapse.A broken line in parallel with the lateral axis indicates the 0 Vstandard and the 0 A standard.

As shown in FIG. 8A, when the voltage dividing resistance R3 is “47 kΩ”,the maximum value of the current value (Iin) is approximately 0.4 A andthus, the charge period is scaled out. In order to specify the temporalchange tendency in each graph in the embodiment 4, simulation analysiswas made with the voltage dividing resistance R3 to be infinite. As aresult, as shown in FIG. 8B, it was confirmed that the temporal changetendencies in the graphs g1, g2, and g3 show the change tendenciessimilar to that in the embodiment 3.

In FIG. 8B, the current value (Iin) flowing into the switching regulator11 during the switching operation gently rises/changes with the timeelapse from the start of the switching operation and reaches the maximumvalue of approximately 0.6 A. It was confirmed that the current value(Iin) after having reached the maximum value changes to the constantstate within the range from 0.6 A to 0.5 A or slightly decreases withthe time elapse, similarly to the embodiment 3. It was confirmed fromthe relative temporal changes of the graph g1 and the graph g2 that thecurrent value (Iin) reaches the maximum value when the charged state ofthe capacitor C1 is in the vicinity of approximately a half of thefull-charged capacity. Moreover, it is known from comparison of thetemporal change tendencies between the graph g1 shown in FIG. 8A and thegraph g1 shown in FIG. 8B that the current value (Iin)increases/decreases in accordance with the intensity relationship of thevoltage dividing resistance R3.

The charge control device 10 of the embodiment can charge the capacitorC1 while the maximum value of the current value (Iin) flowing into theswitching regulator 11 during charging is suppressed in accordance withthe charged state when there is limitation on the current capacity ofthe primary power supply 20 or the current amount capable of supply ofthe battery similarly to the embodiment 3.

Embodiment 3 Block Configuration

FIG. 9 is a diagram showing an example of a block configuration of thecharge control device 10 according to an embodiment 5 (hereinafterreferred to also as “the embodiment”). In the embodiment, the chargecontrol device 10 applies bias voltage Vss from outside of the switchingregulator 11 to the SS terminal. And the charge control device 10according to the embodiment executes current control of supplying aconstant current to the capacitor C1 on the basis of the bias voltageVss and the feedback voltage input into the FB terminal. In the chargecontrol device 10 according to the embodiment, constant current controlof the switching regulator 11 not depending on the charge voltage (Vout)or the capacitor C1 is provided.

The charge control device 10 shown in FIG. 9 includes at least theswitching regulator 11, the inductor element L1, a unit that applies thebias voltage Vss (hereinafter also referred to simply as the “biasvoltage Vss”), and a resistance Rsen.

The bias voltage Vss is a unit that applies the predetermined biasvoltage Vss by connecting to an SS terminal of the switching regulator11, for example. The resistance Rsen is a resistance device with one endconnected to the FB terminal. In the embodiment, the resistance Rsen isprovided between the negative electrode-side terminal of the capacitorC1 constituting a power supply for backup and the GND. The other end ofthe resistance Rsen connected to the FB terminal is grounded to the GNDof the vehicle. In the embodiment, a potential difference between thenegative electrode-side terminal of the capacitor C1 and the GND isdetected as a feedback voltage through the resistance Rsen.

As already described above, the capacitor C1 constitutes a part of thepower supply for backup provided in the power receiving unit of theonboard apparatus. When the potential difference between the negativeelectrode-side terminal of the capacitor C1 and the GND is to benegative-feedback input into the FB terminal by using the resistanceRsen, the charged power is backup supplied to the capacitor C1 includingthe resistor Rsen and the diode element D1. Thus, a resistance value ofthe resistance Rsen that detects the potential difference between thenegative electrode-side terminal of the capacitor C1 and the GND as thefeedback voltage is preferably as small as possible. By making theresistance value of the resistance Rsen small, a load loss of the powerduring the backup operation can be reduced.

The COMP terminal of the switching regulator 11 is grounded to the GNDof the vehicle through a resistance Rt and a capacitor Ct1. In theswitching regulator 11, a switching band during the switching operationis limited on the basis of a time constant determined by a value of theresistance Rt and a value of the capacitor Ct1 connected to the COMPterminal. Since the switching band is limited, low-harmonic oscillationby the phase difference of the voltage change and the current changeduring the switching operation, for example, is suppressed.

In the block configuration shown in FIG. 9, the constitution other thanthe bias voltage Vss and the resistance Rsen is similar to theconstitution in FIG. 1. Hereinafter, the charge control operation of thecharge control device 10 of the embodiment will be described mainly onthe constitution different from that in FIG. 1.

Charge Control Operation

The bias voltage Vss connected to the SS terminal outside the switchingregulator 11 is input into the non-inverted input terminal of the erroramplifier 11 b. Moreover, the potential difference between the negativeelectrode-side terminal of the capacitor C1 and the GND detected throughthe resistance Rsen is input into the inverted input terminal of theerror amplifier 11 b through the FB terminal. As already described, thereference voltage VREF is input into the non-inverted input terminalother than the non-inverted input terminal to which the bias voltage Vssis input in the two non-inverted input terminals of the error amplifier11 b.

In the operation of the error amplifier 11 b, the non-inverted inputterminal with a relatively low voltage value takes preference in thevoltage values input into the two non-inverted input terminals. Here,the voltage value of the reference voltage VREF is set to approximatelyfrom 0.6 to 1.0 V. Therefore, by setting the voltage value of the biasvoltage Vss connected to the SS terminal outside the switching regulator11 to less than the reference voltage VREF, the operation of the erroramplifier 11 b based on the differential voltage (error) between thefeedback voltage input into the FB terminal and the bias voltage Vssinput into the SS terminal is made possible.

The error amplifier 11 b amplifies the differential voltage (error)between the feedback voltage input into the FB terminal and the biasvoltage Vss by the predetermined gain (A) and outputs the amplifieddifferential voltage as an error signal to the output terminal.

In the embodiment, too, the switching regulator 11 generates the gatecontrol signal on the basis of a comparison result between the voltagevalue of the slope waveform input into the inverted terminal of thecomparator 11 d and the output voltage value of the error amplifier 11 binput into the non-inverted terminal. In the embodiment, too, the chargecontrol device 10 can control the current supplied to the capacitor C1through the inductor element L1 during the switching operation, forexample, by controlling the output voltage of the error amplifier 11 bof the switching regulator 11.

Here, a relationship among a current average value (Ichg) of the current(Iout) supplied to the capacitor C1 through the inductor element L1, thebias voltage Vss, and the resistance Rsen is expressed by the followingformula (8):

Ichg=Vss÷Rsen  Formula (8)

※Ichg=Average value obtained by eliminating the ripple of IOUT

As shown in the formula (8), the charge control device 10 according tothe embodiment can control the current average value (Ichg) supplied tothe capacitor C1 through the inductor element L1 during the switchingoperation to the constant current value according to the bias voltageVss and the resistance Rsen.

The resistance value of the resistance Rsen provided between thenegative electrode-side terminal of the capacitor C1 and the GND ispreferably as small as possible in order to suppress the load loss ofthe electricity during the backup operation as described above. As asetting example of the resistance Rsen and the bias voltage Vss, theresistance value of the resistance Rsen at “68 mΩ” and the voltage valueof the bias voltage Vss at “0.1 V” can be presented, for example.

Charge Current Characteristics

FIG. 10 is a diagram shoving an example of the charge currentcharacteristics by the charge control device 10 of the embodiment. Thecharge current characteristics in FIG. 10 are a result of simulationanalysis of the charge control device 10 shown in FIG. 9 assuming thatthe input voltage of the VIN terminal is “5 V”, the bias voltage Vss is“0.1 V”, the resistance Rsen is “68 mΩ”, and the inductor element L1 is“2.2 μH”.

In FIG. 10, a graph g1 shows a temporal change of the average value(Iin) of the current ISW flowing between the VIN terminal and the sourceof the switching element SW1 during the switching operations of theswitching elements SW1 and SW2. A graph g2 shows a temporal change ofthe charge voltage value (Vout) of the capacitor C1, and a graph g3shows a temporal change of the current value (Iout) supplied to thecapacitor C1 through the inductor element L1. A vertical axis in FIG. 10indicates a current value (0.5 A/div) and a voltage value (1 V/div),while a lateral axis indicates normalized time elapse, and a broken linein parallel with the lateral axis indicates the 0 V standard and the 0 Astandard.

As shown in the graph g2, the charge voltage value (Vout) of thecapacitor C1 changes as it gently rises with the rime elapse from thestart of the switching operation and reaches the constant voltage valuedetermined by the charge capacity of the capacitor C1. Moreover, asshown in the graph g3, the temporal change of the current value (Iout)supplied to the capacitor C1 changes in the constant state. It is knownthat regarding the current value (Iout), the current average value(Ichg) acquired by a relational equation expressed by the formula (8)changes around the vicinity of 1.5 A.

From the relative temporal changes of the graph g2 and the graph g3, itis known that the current value (Iout) supplied to the capacitor C1changes in the constant state without depending on the charge voltagevalue (VOut) of the capacitor C1. As shown in the graph g1, it is knownthat the current value (Iin) flowing into the switching regulator 11during the switching operation rises with constant inclination with thetime elapse from the start of the switching operation and reaches thecurrent average value (Ichg) acquired by the relational equationexpressed by the formula (8) as the maximum value.

In the charge control device 10 in she embodiment, the average currentvalue (Ichg) supplied to the capacitor C1 is determined by the biasvoltage Vss input into the SS terminal and the resistance Rsen. In theembodiment, even if a current feedback loop relating to generation ofthe slope waveform described in the embodiment 1 to the embodiment 4 isnot provided, the average current value (Ichg) supplied to the capacitorC1 can be controlled. Thus, the form of the charge control device 10shown in the embodiment 5 can be applied also to a switching regulatorof a voltage mode type, a hysteresis type, and a COT (Constant on Time)type other than the switching regulator of the current mode type.

Embodiment 6 Block Configuration

FIG. 11 is a view showing an example of a block configuration of thecharge control device 10 according to an embodiment 6 (hereinafterreferred to also as “the embodiment”). The charge control device 10shown in FIG. 10 is a form in which the charge voltage (Vout) charged inthe capacitor C1 is further reflected as a feedback amount with respectto the form of the charge control device 10 described in the embodiment5.

In the charge control device 10 in the embodiment, as described in theembodiment 3, for example, the current value (Iin) flowing into theswitching regulator 11 during the switching operation is controlled inaccordance with the charged state of the capacitor C1 by reflecting thecharge voltage (Vout) charged in the capacitor C1 as the feedbackamount.

In the charge control device 10 in the embodiment, even in the caseother than the current-mode-type switching regulator, when the currentcapacity of the primary power supply 20 or the current amount capable ofsupply of the battery is limited, the capacitor C1 can be charged whilethe maximum value of the current value (Iin) flowing into the switchingregulator 11 is suppressed.

The charge control device 10 shown in FIG. 11 includes at least theswitching regulator 11, the inductor element L1, a unit that applies thebias voltage Vss (hereinafter also referred to simply as the “biasvoltage Vss”), the resistance Rsen, and the resistances R1 and R2. Theresistances R1 and R2 detect the charge voltage charged in the capacitorC1. In the block configuration shown in FIG. 11, the constitution otherthan the resistances R1 and R2 is similar to the constitution in FIG. 9.

The one end of the resistance R1 is connected to the positiveelectrode-side terminal of the capacitor C1, while the other end isconnected to the FB terminal. The one end of the resistance R2 isconnected to the negative electrode-side terminal of the capacitor C1,while the other end is connected to the FB terminal. Hereinafter, thecharge control operation of the charge control device 10 of theembodiment will be described mainly on the constitution different fromthat of FIG. 9.

Charge Control Operation

In the switching regulator 11 in FIG. 11, the charge voltage (Vout) ofthe capacitor C1 detected through the resistance (R1, R2) and thepotential difference between the negative electrode-side terminal of thecapacitor C1 and the GND detected through the resistance Rsen is inputas the feedback voltage into the inverted input terminal of the erroramplifier 11 b.

The voltage value of the bias voltage Vss connected to the SS terminaloutside the switching regulator 11 is set to a voltage value less thanthe reference voltage VREF. The bias voltage Vss applied to the SSterminal is input into the non-inverted input terminal of the erroramplifier 11 b.

The error amplifier 11 b amplifies the differential voltage (error)between the feedback voltage input onto the FB terminal and the biasvoltage Vss by the predetermined gain (A) and outputs the amplifieddifferential voltage as an error signal to the output terminal.

The relationship of the embodiment among the current average value(Ichg) of the current (Iout) supplied to the capacitor C1 through theinductor element L1, the charge voltage (Vout) of the capacitor C1, thebias voltage Vss, the resistance Rsen, the resistance (R1, R2) isexpressed by the following formula (9):

$\begin{matrix}{\mspace{79mu} {{{Ichg} = \frac{{Vss} - {\frac{R\; 2}{R\; 1} \times \left( {{Vout} - {Vss}} \right)}}{Rsen}}{{{Ichg}} = {{Average}\mspace{14mu} {value}\mspace{14mu} {obtained}\mspace{14mu} {by}\mspace{14mu} {eliminating}\mspace{14mu} {the}}}{{ripple}\mspace{14mu} {of}\mspace{14mu} {IOUT}}}} & {{Formula}\mspace{14mu} (9)}\end{matrix}$

As shown in the formula (9), the charge control device 10 according tothe embodiment can control the current average value (Ichg) supplied tothe capacitor C1 through the inductor element L1 during the switchingoperation to a constant current value according to the bias voltage Vss,the resistance Rsen, and the charge voltage (Vout) of the capacitor C1detected through the resistances R1 and R2.

Charge Current Characteristics

FIG. 12 is a diagram showing an example of the charge currentcharacteristics by the charge control device 10 of the embodiment. Thecharge current characteristics in FIG. 12 are a result of simulationanalysis of the charge control device 10 shown in FIG. 11 assuming thatthe input voltage of the VIN terminal is “5 V”, the bias voltage Vss is“0.1 V”, the resistance Rsen is “68 mΩ”, the resistance R1 is “82 kΩ”,the resistance R2 is “1 kΩ”, and the inductor element L1 is “2.2 μH”.

In FIG. 12, a graph g1 shows a temporal change of the average value(Iin) of the current ISW flowing between the VIN terminal and the sourceof the switching element SW1 during the switching operations of theswitching elements SW1 and SW2. A graph g2 shows a temporal change ofthe charge voltage value (Vout) of the capacitor C1, and a graph g3shows a temporal change of the current value (Iout) supplied to thecapacitor C1 through the inductor element L1. A vertical axis in FIG. 12indicates a current value (0.5 A/div) and a voltage value (1 V/div),while a lateral axis indicates normalized time elapse, and a broken linein parallel with the lateral axis indicates the 0 V standard and the 0 Astandard.

As shown in the graph g1, the current value (Iin) flowing into theswitching regulator 11 during the switching operation gentlyrises/changes with the time elapse from the start of the switchingoperation and reaches the maximum value of approximately 0.7 A. Thecurrent value (Iin) after having reached the maximum value changes inthe constant state within the range from 0.7 A to 0.5 A or slightlydecreases with the time elapse.

As shown in the graph g2, the charge voltage value (Vout) of thecapacitor C1 changes to gently rise with the time elapse from the startof the switching operation and reaches the constant voltage valuedetermined by the charge capacity of the capacitor C1. It is known fromrelative temporal changes in the graph g1 and the graph g2 that thecurrent value (Iin) reaches the maximum value when the charged state ofthe capacitor C1 is in the vicinity of approximately a half of thefull-charged capacity. Moreover, by comparing the temporal changetendency of the graph g1 shown in FIG. 10 with the temporal changetendency of the graph g1 shown in FIG. 12, it is known that relativeintensity of the current value (Iin) flowing into the switchingregulator 11 during the switching operation is suppressed.

As shown in the graph g3, the temporal change of the current value(Iout) supplied to the capacitor C1 lowers with constant inclinationwith the time elapse from the start of the switching operation andchanges to reach the current value (Iin) flowing into the switchingregulator 11 during the switching operation. It is known from therelative temporal changes in the graph g3 and the graph g2 that thecurrent value (Iin) flowing into the switching regulator 11 decreaseswith the increase of the charge voltage value (Vout) of the capacitorC1.

FIG. 13 is a diagram of another example of the charge currentcharacteristics by the charge control device 10 of the embodiment. FIG.13 is a result of simulation analysis of the charge control device 10shown in FIG. 11 with the resistance R1 at “220 kΩ” and the otherconditions similar to those in FIG. 12 in order to check a degree ofcontribution of the resistance R1 to the charge current characteristics.The graphs g1, g2, and g3, the vertical axis, the lateral axis, the 0 Vstandard, and the 0 A standard shown in FIG. 13 are similar to those inFIG. 12.

As shown in the graph g1, the current value (Iin) flowing into theswitching regulator 11 during the switching operation rises/changes withthe time elapse from the start of the switching operation and reachesthe maximum value of approximately 1.1 A. As shown in the graph g3, thetemporal change of the current value (Iout) supplied to the capacitor C1lowers with constant inclination with the time elapse from the start ofthe switching operation and changes to reach the current value (Iin)flowing into the switching regulator 11 during the switching operation.

It is known from comparison of the temporal change tendencies betweenthe graphs g1 and g2 shown in FIG. 12 and the graphs g1 and g2 shown inFIG. 13 that a rise change of the current value (Iin) from the start ofthe switching operation gets closer to the linear constant inclinationwith an increase in the resistance value of the resistance R1. It isknown that the maximum value the current value (Iin) reaches increaseswith the increase of the resistance value of the resistance R1.Moreover, with the increase of the resistance value of the resistanceR1, the constant inclination of the temporal change of the current value(Iout) supplied to the capacitor C1 decreases.

Variation Block Configuration

FIG. 14 is a diagram showing an example of a block configuration of thecharge control device 10 according to a variation. It was described inthe form shown in the embodiment 5 and the form shows in the embodiment6, in the charge control device 10, the charge current supplied to thecapacitor C1 constituting the power supply for backup can be controlledon the basis of the bias voltage Vss and the feedback voltage. In thecharge control device 10 of the variation, the resistance Rsen isprovided between the inductor element L1 and the positive electrodeterminal of the capacitor C1, and the constant current control isexecuted by using a potential difference generated in the resistanceRsen.

The charge control device 10 of the variation includes at least theswitching regulator 11, the inductor element L1, the resistance Rsen,the resistances R1, R2, R3, R4, R5, and R6. In the block configurationshown in FIG. 14, the constitution other than the resistance Rsen andthe resistances (R1 to R6) is similar to the constitution in FIG. 9. Theswitching regulator 11 in FIG. 14 is simplified.

Charge Control Operation

In FIG. 14, one end of the resistance Rsen is connected to the outputend of the inductor element L1, while the other end is a connected tothe positive electrode-side terminal of the capacitor C1. One end of theresistance R1 and the output end of the inductor element L1 areconnected, while the other end of the resistance R1 and the FB terminalof the switching regulator 11 are connected. Moreover, the other end ofthe resistance R2 with one end grounded to the GND of the vehicle andthe FB terminal of the switching regulator 11 are connected. The otherend of the resistance R6 with one end connected to the positiveelectrode-side terminal of the capacitor C1 and the FB terminal of theswitching regulator 11 are connected.

The voltage of the resistance Rsen provided between the inductor elementL1 and the positive electrode terminal of the capacitor C1 on the outputend side of the inductor element L1 is input as the feedback voltage tothe FB terminal of the switching regulator 11 through the resistances R1and R2. The charge voltage (Vout) charged in the capacitor C1 isreflected in the feedback amount by the resistance R6.

Moreover, in FIG. 14, the one end of the resistance R3 is connected tothe positive electrode-side terminal of the capacitor C1, while theother end of the resistance R3 is connected to the SS terminal of theswitching regulator 11. The other end of the resistance R4 with one endgrounded to the GND of the vehicle is connected to the SS terminal ofthe switching regulator 11. The other end of the resistance R5 with oneend connected to the voltage (VIN) supplied by the primary power supply20, not shown, is connected to the SS terminal of the switchingregulator 11.

The voltage of the resistance Rsen provided between the inductor elementL1 and the positive electrode terminal of the capacitor C1 on thepositive electrode terminal side of the capacitor C1 is input as thebias voltage Vss into the S3 terminal of the switching regulator 11through the resistances R3 and R4. An offset voltage for offsetting thebias voltage Vss is supplied by the resistance R5.

In the charge control device 10 of the variation, the potentialdifference detected through the resistance Rsen provided between theinductor element L1 and the positive electrode terminal of the capacitorCI is applied by the resistances (R1 to R4) between the SS terminal andthe FB terminal of the switching regulator 11. Moreover, in the chargecontrol device 10 of the variation, the bias voltage Vss is offset bythe resistance R5. The charge voltage (Vout) charged in the capacitor CIis reflected by the resistance R6 in the feedback amount. Hereinafter,the charge control operation of the charge control device 10 of thevariation will be described mainly on the constitution different fromthat in FIG. 9.

Charge Control Operation

In the form of the variation, the feedback voltage is input into theinverted input terminal of the error amplifier 11 b of the switchingregulator 11. Moreover, the offset bias voltage Vss is input into thenon-inverted input terminal of the error amplifier 11 b. The voltagevalue of the offset bias voltage Vss is set through the resistances R3,R4, and R5 so as to be less than the reference voltage VREF.

The error amplifier 11 b amplifies the differential voltage (error)between the feedback voltage input into the inverted input terminal andthe offset bias voltage Vss by the predetermined gain (A) and outputsthe amplified differential voltage as the error signal to the outputterminal.

In FIG. 14, the resistance values of the resistance R1 and theresistance R3 are set to the same value, and the resistance values ofthe resistance R2 and the resistance R4 are set to the same value. Inthe form of the variation, the switching regulator 11 performs thecontrol operation under the setting conditions such that a voltage ofR1/R2 times of the offset voltage value is generated in the resistanceRsen provided between the inductor element L1 and the positive electrodeterminal of the capacitor C1. As a result, in the charge control device10 of the variation, too, the constant current control is made possiblesimilarly to the form shown in the embodiment 5.

Moreover, by reflecting the charge voltage (Vout) charged in thecapacitor C1 in the feedback amount by the resistance R6, the currentvalue (Iin) flowing into the switching regulator 11 during the switchingoperation can be controlled in accordance with the charged state of thecapacitor C1. In the charge control device 10 of the variation, too, thecapacitor C1 can be charged while the maximum value of the current value(Iin) flowing into the switching regulator 11 is suppressed similarly tothe form shown in the embodiment 6.

Charge Current Characteristics

FIGS. 15 and 16 are diagrams for explaining the charge currentcharacteristics of the variation. FIG. 15 is charge currentcharacteristics of the variation in the form not including theresistance R6, and FIG. 16 is charge current characteristics of thevariation in the form including the resistance R6. In FIGS. 15 and 16,the graph indicated by a solid line expresses the temporal change of theaverage value (Iin) of the current ISW flowing between the VIN terminaland the source of the switching element SW1 during the switchingoperations of the switching elements SW1 and SW2. A graph indicated by atwo-dot chain line expresses the temporal change of the charge voltagevalue (Vout) of the capacitor C1. A graph indicated by a one-dot chainline expresses the temporal change of the current value (Iout) suppliedto the capacitor C1 through the inductor element L1. A vertical axis ineach of FIGS. 15 and 16 indicates a current value (0.25 A/div) and avoltage value (1 V/div), while a lateral axis indicates time elapse(unit time: 5 sec).

As shown in the graph of the one-dot chain line in FIG. 15, the currentvalue (Iout) supplied to the capacitor C1 through the inductor elementL1 shows a change tendency of decreasing with the increase of the chargevoltage value (Vout) of the capacitor C1 indicated by the graph of thetwo-dot chain line. Moreover, as shown in the graph by the solid line,she current value (Iin) flowing into the switching regulator 11 duringthe switching operation shows a change tendency of rising/changing withthe time elapse from the start of the switching operation and reachingthe maximum value in the vicinity of 0.9 A.

Moreover, in the form including the resistance R6, as shown in the graphof the solid line in FIG. 16, the current value (Iin) flowing into theswitching regulator 11 during the switching operation shows a changetendency of rising/changing with the time elapse from the start of theswitching operation and reaching the maximum value. Moreover, thecurrent value (Iin) after having reached the maximum value shows atendency of a constant state in the vicinity of the maximum value or ofdecreasing/changing with the time elapse. In the form including theresistance R6, the maximum value of the current value (Iin) flowing intothe switching regulator 11 during the switching operation shows atendency of being suppressed to less than 0.5 A.

1. A charge control device including a switching regulator that chargesa capacitor with electricity supplied from a power supply, the chargecontrol device comprising: feedback unit that feedback-inputs apredetermined control amount into the switching regulator; and controlunit included in the switching regulator, the control unit controlling acharge current supplied to the capacitor in accordance with the controlamount feedback-input by the feedback unit.
 2. The charge control deviceaccording to claim 1, wherein the feedback unit has a detectionresistance that detects a charge current supplied to the capacitor andfeedback-inputs a potential difference generated at both ends of thedetection resistance to the switching regulator; and the control unitcontrols the charge current supplied to the capacitor on the basis of adifferential voltage between the feedback-input potential differencegenerated at both ends of the detection resistance and a referencevoltage value.
 3. The charge control device according to claim 1,wherein the feedback unit has the detection resistance provided on adownstream side of the capacitor and feedback-inputs a voltage value onan upstream side of the detection resistance to the switching regulator.4. The charge control device according to claim 1, wherein the switchingregulator has a soft start terminal that operates a sent start functionduring a switching operation; and the control unit controls a chargecurrent supplied to the capacitor on the basis of a differential voltagebetween a bias voltage value applied to the soft start terminal and thefeedback-input voltage value on the upstream side of the detectionresistance.
 5. The charge control device according to claim 1, whereinthe switching regulator has a soft start terminal that operates a softstart function during a switching operation; the feedback unit has thedetection resistance provided on an upstream side of the capacitor andfeedback-inputs a first voltage value obtained by dividing a voltagevalue on the upstream side of the detection resistance into thereference voltage value or less to the switching regulator, whileapplying a second voltage value obtained by dividing the voltage valueon a downstream side of the detection resistance to the referencevoltage value or less to the soft start terminal; and the control unitcontrols a charge current supplied to the capacitor on the basis of adifferential voltage between the second voltage value applied to thesoft start terminal and the feedback-input first voltage value.
 6. Thecharge control device according to claim 5, wherein the feedback unitsets a pressure dividing ratio of the first voltage value and a pressuredividing ratio of the second voltage value to an equal ratio and offsetsthe second voltage value.
 7. The charge control device according toclaim 1, wherein the switching regulator is a current-mode-typeswitching regulator, the feedback unit has a detection resistance thatdetects a charge current supplied to the capacitor and feedback-inputs apotential difference generated at both ends of the detection resistanceto the switching regulator; and the control unit controls the chargecurrent supplied to the capacitor so that a differential voltage betweenthe feedback-input potential difference generated at both ends of thedetection resistance and the reference voltage value becomes apredetermined voltage value.
 8. The charge control device according toclaim 1, wherein the feedback unit detects a charge voltage of thecapacitor and feedback-inputs the detected charge voltage to theswitching regulator; and the control unit controls the charge currentsupplied to the capacitor in accordance with the charge voltagefeedback-input by the feedback unit and suppresses a peak value ofcurrent consumption of the switching regulator within a predeterminedvalue.